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Muscular System/, Leslie Vieyra , p.2 - Coggle Diagram
Muscular System/, Leslie Vieyra , p.2
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sarcomere: Myofibrils are made up of many units called sarcomeres, joined end-to-end
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I bands (light bands) are made up of actin filaments, which are anchored to the Z lines
The M line, in the center of the H zone, consists of proteins that hold the myosin filaments in place
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In the center of the A band is the H zone, which consists of myosin filaments only
neuromuscular junction
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Each skeletal muscle fiber (cell) is functionally (not physically) connected to the axon of a motor neuron, creating a synapse
The neuron communicates with the muscle fiber by way of chemicals called neurotransmitters, which are released at the synapse
The cytoplasm of the distal end of the motor neuron contains numerous mitochondria and synaptic vesicles storing neurotransmitters
The muscle fiber membrane in this area contains a specialized region called the motor end plate, in which the sarcolemma is tightly folded
When an electrical impulse reaches the end of the axon of a motor neuron, synaptic vesicles release neurotransmitter into the synaptic cleft, the gap between the membranes of the neuron and muscle fiber
The neurotransmitters diffuse across the cleft, bind to the motor end plate, and stimulate the muscle fiber to contract
sliding filament theory of muscle contraction: The sliding filament theory explains the mechanism of muscle contraction based on muscle proteins that slide past each other to generate movement.
- relaxed muscle/ a muscle contraction starts in the brain
- exposed binding sites on the actin allow the muscle contraction cycle to occur
- myosin heads bind to actin, forming cross bridges , connecting myosin to actin
- ADP and P release from myosin and cross bridges pull thin filaments
- New ATP binds to myosin, breaking the connection to actin
- ATP splits, which provides power to "cock" the myosin heads and store energy for the next power stroke
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muscle coverings
Fascia blends with the epimysium, the layer of connective tissue around each skeletal muscle
The perimysium extends inward from the epimysium; it surrounds bundles of skeletal muscle fibers, called fascicles, within each muscle
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